PROJECT SUMMARY Amyotrophic lateral sclerosis (ALS) is one of the most devastating neurodegenerative diseases and no therapies significantly extend patient lives. Thus, new therapeutics to treat ALS are needed. QurAlis is approaching this need by correcting the hyperexcitability that leads to motor axon neuropathy and neurodegeneration. This hyperexcitability is linked to deficits in the delayed-rectifier potassium (K+) current conducted by Kv7.2/7.3 voltage-gated ion channels. Approximately 50% of ALS patients have significant hyperexcitability in their motor cortex and spinal motor neurons and can be identified using neurophysiological biomarkers. Retigabine, an anti- epileptic and positive modulator of Kv7.2/7.3, has recently been shown to reverse this hyperexcitability in a clinical trial of ALS patients but unfortunately, is associated with off-target effects and is no longer available. QurAlis?s goal is to produce a more potent and specific Kv7.2/7.3 activator. In Phase I, Aim 1, we will develop a protocol for transcriptional reprogramming-based production of iMNs. In Aim 2, we will validate the iMNs cellular properties compared to iMNs programmed using standard patterning factors and will validate the electrical properties of iMNs using the OptopatchTM platform. In Aim 3, we will produce a large-scale cryopreserved bank of iMN. At Phase I conclusion, we will have achieved an iMNs purity >80% and demonstrated that these cells are electrically active and have a concentration-dependent reduction in neuronal activity in response to retigabine with an EC50 between 1 and 5 M. In addition, we will have iMN production at a sufficient scale to perform chemical structure-activity relationship screening (e.g., frozen batches of at least 150 million cells). In Phase II, Aim 4, we will develop new chemical matter and test compounds for their ability to modulate Kv7.2/7.3 in structure-activity assays, and in Aim 5 we will identify compounds that reduce excitability in patient-derived iMNs. At conclusion of Phase II, we will have identified 10-20 compounds that meet our target product profile for on- target and off-target potency (Aim 4 milestone) and we will have two or more compounds that shift Kv7.2/7.3 activity in patient-derived iMNs toward reduced excitability at an effect size greater or equal to retigabine at its clinically efficacious dose of 2 M. Aim 5 milestone). We have preliminary data demonstrating that our approach and goals are feasible: we have 3 independent novel chemical scaffolds that are potent activators of Kv7.2/7.3 whose activity has been validated in both heteromeric ion channels and in patient-derived MNs (traditional protocol) using the Optopatch platform. At conclusion of this study, we will have identified several lead compounds that are ready for ADME, PK, and non-GLP toxicology studies, and we will have a scaled-up protocol for producing patient-derived iMNs that will facilitate future drug development that target other pathways in ALS patients (e.g., autophagy).